1. Field of the Invention
The present invention relates to an information apparatus, such as a personal computer, and, more particularly, to an information apparatus separable into a main apparatus and a subsidiary apparatus.
2. Description of the Related Art
Along with a trend toward downsizing, various portable information apparatuses have been developed, for example, notebook-type computers and handy terminals. However, the conventional way of downsizing for such portable information apparatuses is not altogether satisfying. Some portable information apparatuses partially give up performance and functions in exchange for downsizing, reducing the ease of operation or the freedom to construct systems with other apparatuses.
Recently, some personal computers employ pen-base input means, instead of keyboards, which also substantially impede the downsizing of such computers. Such a pen-base computer has an input digitizer provided on a display such as a liquid crystal display (LCD). The trace of the pen is inputted by means of the digitizer, and displayed on the display as it is actually drawn by the user. Thus, a user can input data thereto just like writing on a sheet of paper. The direction of data input or display can also be changed as desired.
However, in a separable system, either a portable computer system or a pen-base computer, comprising a main computer apparatus and a subsidiary apparatus which are connected by a connecting cord, it is troublesome to connect or disconnect the connecting cord. Moreover, the cord may obstruct a user's easy operation.
Further, when a portable system is transported or left unused, the connector portions of the main and subsidiary (node) apparatuses are likely to be contaminated with dust or the like. Thus, reliability of the connector portions is poor. Such connector portions may be provided with covers, but such covers must be opened or shut each time the main and subsidiary apparatus are connected or disconnected.
Similarly, a pen-base computer suffers poor reliability of the connector portions. Because it is used in various locations and the subsidiary apparatus is connected to the main apparatus in various manners (input directions), the connector portions are frequently subjected to dust or the like.
Further, a conventional pen-base computer is not provided with means for achieving attachment and detachment of the subsidiary apparatus in manners suitable for the respective input directions. Still further, a pen-base computer is not provided with means for attaching the subsidiary apparatus to the main apparatus in such a manner that the display is easy to see if the computer is connected to a keyboard for facilitating inputting a large amount of data. Therefore, various inconveniences are caused.
Further, in a pen-base computer, a key board connector is provided in the subsidiary apparatus, not in the main apparatus. In many cases, the main apparatus and separate subsidiary apparatuses exchange data by means of buses connected by interface cables. However, because many connector pins for such cables are required, it is not easy to connect or disconnect the cables.
The main apparatus and a subsidiary apparatus can be connected by one pair of data cables (optical cables) by using non-contact optical communication, which enables high-speed data communication therebetween. This communication method facilitates connecting one main apparatus to one or more subsidiary apparatuses (nodes) or one subsidiary apparatus to a plurality of devices. This optical communication protocol normally uses polling selecting scheme. The CSMA/CD, which is widely used for network schemes including collision detection, is normally avoided because the CSMA/CD will slow down the communication process.
In the polling selecting scheme, a computer always serves as a main apparatus. More specifically, the computer always polls a subsidiary apparatus first, and the subsidiary apparatus responds to the polling. For example, if the computer is connected to a subsidiary apparatus, such as a keyboard, requiring the computer to periodically determine whether there has been an input therefrom, the computer periodically sends a polling signal to the keyboard inquiring whether there has been a key input and which key has been pressed, and the keyboard, that is, the subsidiary apparatus, answers the inquiry. The keyboard is not provided with means for spontaneously informing the main apparatus of a key input without receiving an inquiry from the main apparatus. If the computer is connected to a subsidiary apparatus, such as a floppy disk drive (FDD), which requires an instruction from the computer, the computer outputs an access instruction to the FDD, and the FDD reads data from the floppy disk and outputs the data to the computer, or writes data from the computer onto the floppy disk (selecting). Because a computer always operates as a main apparatus in the polling selecting scheme, the scheme prevents collision between instruction signals and therefore simplifies the protocol.
However, because the above-described conventional scheme requires the main apparatus to always make polling for detecting the status of each I/O and exchanging data with a subsidiary apparatus, the main apparatus must keep polling even when the main and subsidiary apparatuses are separated from each other and each apparatus operates independently. Therefore, electricity is continuously consumed by the CPU operation and communication controlling units, and the light emitting and receiving units.